1. Field of the Disclosure
The present invention relates to display devices, and more particularly to a display device having a touch sensor in which influence of noise from a display device is reduced for minimizing a touch error; and a method for driving the same.
2. Discussion of the Related Art
These days, the touch sensor which can input information by touching a screen of various display devices is widely applied to a computer system as an information input device. Since the touch sensor enables a user to move or select displayed information by simple touch of the screen with a finger or a stylus s, everybody can use the touch sensor, easily.
The touch sensor provides touch information by sensing a touch and a touch position on the screen of the display device, and the computer system analyzes the touch information to carry out an order. As the display device, flat display devices, such as liquid crystal display devices, plasma display panels, organic luminescence diode display device, and the like are used, mostly.
Depending on sensing principles, in touch sensing technologies, there are a resistance film type, a capacitive type, optical type, an infrared rays type, an ultrasonic type, and an electro-magnetic type.
The resistance film type touch sensor perceives the touch by sensing a change of voltage taken place as upper and lower resistance films (Transparent conductive films) are brought into contact by a touch pressure. However, the resistance film type touch sensor has drawbacks in that the touch sensor or the display device is susceptible to the touch pressure, and transmissivity is low due to an optical scattering effect of an air layer between the resistance films.
The capacitive type touch sensor which can supplement the drawbacks of the resistance film type touch sensor perceives the touch by sensing a change of capacitance taken place as a small amount of charge moves to a touch point when a conductive body, such as a human body or the stylus, touches. The capacitive type touch sensor is paid attention since the capacitive type touch sensor has a long life time, high transmissivity, and an excellent touch sensing capability, and enables multiple touches owing to reinforced glass applied thereto.
In general, the touch sensor is fabricated as a panel attached to an upper side of the display device for performing a touch input function. However, the display device having the touch sensor attached thereto has a problem in that the touch sensor malfunctions due to a noise component from the display device.
In the meantime, if a liquid crystal display device is used as the display device, the liquid crystal display device is operative in a TN (Twisted Nematic) mode, or a VA (Vertical Alignment) mode, which uses a vertical electric field, or an IPS (In-Plane Switching) mode or an FFS (Fringe Field Switching) mode, which uses a horizontal electric field.
The TN mode, or the VA mode liquid crystal display device which uses the vertical electric field has a common electrode formed throughout an upper substrate for shielding the noise from the liquid crystal display device. Opposite to this, since the IPS mode or the FFS mode liquid crystal display device which uses the horizontal electric field has the common electrode formed on a lower substrate together with pixel electrodes, shielding of the noise infiltrating into the touch sensor from the liquid crystal display device is difficult.